Why is the current bird flu so deadly?

What’s making the latest strain of bird flu so deadly? Avian influenza used to mostly affect poultry, and while it continues to decimate poultry populations around the world, the latest strain, H5N1, is spreading widely among wild birds. It also seems to be spreading to mammals more frequently.

“Something is quite different about this virus this go around,” Rebecca Poulson, a wildlife disease researcher at the University of Georgia, told Nature.

Researchers aren’t sure why the current outbreak hasn’t disappeared, but they believe mutations may have increased its ability to replicate or to infect a broader range of species.

Read more in Nature.